The country watched with bated breath to see whether a Brexit deal will finally make it through Parliament, but things didn't go the way Boris Johnson had planned.
Sir Oliver, who lost the Tory whip for voting against the Government on Brexit previously, said the amendment was "insurance" against the UK crashing out of the EU without a deal by mistake on the scheduled deadline of October 31.
What happens now?
Under the terms of the so-called Benn Act, Mr Johnson must write to the EU asking for a three-month Brexit extension if he has not secured a deal by 11pm UK time on October 19.
However, it's been revealed the PM has written to MPs on Saturday evening asserting he will not negotiate an extension on the deal.
If he doesn't comply with the Benn Act or Letwin amendment, campaigners would likely mount a legal challenge which could see a potential Supreme Court hearing within days.
What is likely to happen next then?
In the light of the amendment, the prime minister decided not to have a so-called "meaningful vote" on his deal - the legislation needed for Brexit.
Instead, the Government is set to bring the Withdrawal Agreement Bill to the Commons early next week.
A "meaningful vote" could be held early next week if Speaker John Bercow allows it, however Commons leader Jacob Rees-Mogg has already said the Government is planning to give MPs a chance to have a meaningful vote on the Brexit deal on Monday.
Could Boris Johnson still get his deal through Parliament?
Yes, but time is running out ahead of the October 31 deadline, as the European Parliament would also need to ratify it.
Without a meaningful vote, support for the agreement has not yet been tested.
Though the PM has attracted support from a number of prominent Brexiteer Tories, the DUP is strongly opposed to the deal.
ITV News Political Editor Robert Peston said the DUP was the make-or-break for Saturday's vote.
Would the EU agree to an extension?
Despite European Commission President Jean-Claude Juncker raising doubts over another Brexit delay, the decision needs to be taken by all 27 remaining EU states, not him.
According to ITV News Correspondent Angus Walker, the EU may not be totally opposed to an extension if it means avoiding a no-deal.
However, the EU could set a different length to an extension, either shorter or longer than the three-month one cited in the Benn Act.
The EU could decide not to formally respond to such a letter from the PM until it sees if Mr Johnson can get the Withdrawal Agreement Bill through Parliament next week.
If the PM gets the Withdrawal Agreement Bill through, there could be a special gathering of EU leaders on October 28.
If the deal needs more time at the stage to get through Parliament, EU leaders could agree to a short extension.